Bitcoin Forum

Hey guys,

So the bug finally bit me. I've been mostly buying bitcoins, but want to supplement it with some mining. I have about $4000 in Newegg credit I want to use. I need the best mobo, power supply, cables, etc to power 3 to 4 6990. I think i want to go open instead of spending money on a case.

Saw this thread. Some of the info here is outdated. I'm looking to run Windows 7.

https://en.bitcoin.it/wiki/Mining_rig#Three_ATI_6990s.2C_Approximately_2.1_Ghash.2Fs

I know I can get a kick ass rig with $4000. Any help you guys can extend is greatly appreciated. :)

btw, willing to make btc contributions the right consultant  ;D

From what I have read and seen on this forum, you would probably be better of with 5970's than 6990's. As for a mobo, might want
to check this one out....http://www.newegg.com/Product/Product.aspx?Item=N82E16813128508



-ST

As said above 5970 is superior to 6990.  Not sure if you already bought the 6990 but if you haven't (or can still return them) get 5970s instead.  For the 5970 just get ATI brand.  They are the most common and are all "reference" design They are getting hard to find but are priced $400 to $500 which is far better peformance per watt.

If you intend to run 3x per rig then go w/ 1200W or 1350W powersupply from Seasonic or Enermax.  If you want to run 4x per rig then forget high end powersupply and just look for 2x 750W units.

For 3x 5970 (or 6990) IMHO the best Motherboard is the Gigagbyte P67A-UD7-B3.  Due to the spacing of 16x slots you can run 3 video cards (6 GPU) without need for any extender cables.  Drop in 2GB of ram, sempron CPU, and a 4GB flash usb drive and you are ready to run a dedicated linux rig.

If you want to run 4x (or more) per rig then you need to look into using extenders, etc.

WOW if you are considering starting mining at this point in time then you might as well donate the money to charity mate. You are only going to fail. Mining has had its time. All my rigs are off and I am still losing money as the hardware depreciates. DON'T buy mining rigs right now. You have been warned !

Why?  3x5970 rig would run $1800 ish (if OP can find a $400 5970 deal it would be ~$1500).  With free electricity 3x5970 throw off ~$180 per month at current difficulty & price.

Now the "boom miners" would say WTF that is nearly 10 months to break even.  Of course anyone in the real world knows the "boom" wasn't sustainable.  $180 per month on $1800 hardware is a 10% monthly return.

If the OP goal is to simply use mining to buy bitcoins then in 1 year his rig would produce 478BTC (at current difficulty) or an amortized cost of $3.78 per BTC.  Of course it isn't like his rig exploded at the end of the year so lifetime cost could be much lower.  Now if OP doesn't have free power then that raises his cost but it COULD still be cheaper than buying them on the market.

Since OP intends to speculate in BTC then the volatility of BTC is a non-issue (it affects him equally if he mines or buys).  The largest risk is inability to predict future difficulty.  If difficulty shot up significantly it would make his ammortized coin cost higher however difficulty has been declining recently and likely will for some time.

There are risks but to say he should donate it to charity (predicting a 100% loss) is just stupid.

Yes no risks at all. What if BTC value drops to <$1 ??? Never took that into account, did you.

I never said no risks at all.  I outlined plenty of risks however ..... HE INTENDS TO SPECULATE IN BITCOINS!!!!!!!!

Thus the exchange rate risk is the SAME if he mines coins or buys coins.

If he INTENDS to hold bitcoins (as a speculative investment) then either way he is buying coins and the exhcnange rate risk is the same.

Mining coins = buying coins w/ hardware + electricity
Buying coins = buying coins w/ fiat money

Given exchange rate risk is the same it is a non-issue if he intends to speculate.

The only question becomes which is the cheaper method to generate coins.

At no electricity a triple 5970 rig would produce 380 coins in first year at an ammortized cost of ~$3.75 per coin.  If the average bitcoin price over next year is <$3.75 then it is cheaper to buy them on the market.  If it is higher than it is cheaper to mine them.  However hardware will likely last much longer than a year.  The longer the hardware lasts the lower the ammortized cost per coin. 

Back on topic,
You cant run more than 4 GPU's on a Windows machine. I have a 6990 and a 5830 in one rig and the 6990 puts off way to much heat to even consider three or four of them together. You should be able to run several 6990 in an open "case" if you have a cool environment and suitable fans blowing on them. You would however not be able to run Windows, you would need to run a distribution of Linux.

That hasn't been true for sometime now.  The windows GPU limit was raised to 8 (why they even have a GPU limit i don't know) many driver versions ago.  I am typing this on a Windows 7 workstation w/ 3x watercooled 5970s (6GPUs).

I stand corrected.

Wait for the new 7800 series which is about to drop. I bet they wont be too expensive and pull 700-800m/hash alone. 6990 are for idiots with more money than sense. 2x 5850/5870/6950/6970's will all beast a 6990. Sorry but its true. 4 cards in one mobo is fine and you wont get problems. YOu need extenders with power molex's on otherwise as each PCI-E draws 75W and you can fry motherboards this way. I did a gigabyte :)

Cheap mobo with 4 PCI-E slots (use 1x to 16x extenders), cheap ram,Cheap CPU, Corair AX1200 or Antec HCP1200 (i use on 1 of mine), and good cooling :) Dependant on how many your setting up, i have 8 5850's all doing 400m/hash (2 rigs) and they each cost me around £900 max each, you'll need get the hot air away. I use OTT 12" 1440m3 fan pumping all the air out the room which does awesome and is quiet. This becomes more of an issue the more you add rigs, obviously :)

Power supply is your only issue and if you wait for 7800's, you may get away with a cheaper supply. I reccomend them 2 supplys for a GOOD REASON. I also reccomend a UPS system but that gets expensive but it will give your systems a nice clean steady current. My cards run 115amp and my PSU is 98 (corsair 100amp) so i was looking into it. Not cheap. THats purely optional. But your hardware could last longer for this also.

Corsair AX1200 though, is the best single 12V rail PSU out there, the Antec is 8... or 12..... cant remember but a single rail 1200W PSU is some achievement!